Beginning with version 1.50, PDFsharp/MigraDoc should work under Medium Trust. But since Medium Trust prevents access to the fonts installed with the operating system, you will have to use a font resolver and include the fonts you need with your application, assuming you are using the Core build.

This issue was solved with PDFsharp 1.50. Table rendering still takes some time and maybe there will be some smaller optimizations in the future, but version 1.50 is much faster than version 1.32 and earlier versions.